Sue Hemming, CPS Director of Legal Services, said: “During the weekend of 4 March 2018 in Salisbury the former Russian spy Sergei Skripal and his daughter Yulia were poisoned with a military-grade nerve agent of a type developed by Russia, part of a group of nerve agents known as ‘Novichok’.

“A police officer, DS Nick Bailey, who was involved in searching the Skripal’s home address after this attack, was also poisoned with the same nerve agent.

“The Counter Terrorism Policing Network has conducted a thorough investigation into how this attack happened. They have recently submitted a file of evidence to the Crown Prosecution Service so we could make a decision whether criminal charges could be brought against anyone who was involved in these events.

“Prosecutors from CPS Counter Terrorism Division have considered the evidence and have concluded there is sufficient evidence to provide a realistic prospect of conviction and it is clearly in the public interest to charge Alexander Petrov and Ruslan Boshirov.

“A realistic prospect of conviction means the CPS is satisfied on an objective assessment that the evidence can be used in court and that an objective, impartial and reasonable jury hearing the case, properly directed and acting in accordance with the law, is more likely than not to convict these two individuals of the charges. It is of course for a jury to decide whether the evidence is enough for them to be sure of the suspects’ guilt.”

Ms Hemming added: “We will not be applying to Russia for the extradition of these men as the Russian constitution does not permit extradition of its own nationals. Russia has made this clear following requests for extradition in other cases. Should this position change then an extradition request would be made.

“We have, however, obtained a European Arrest Warrant which means that if either man travels to a country where an EAW is valid, they will be arrested and face extradition on these charges for which there is no statute of limitations.”